The present invention relates to a thin-film magnetic head having magneto-resistive effect elements, or in particular to a structure and a method of manufacturing a thin-film magnetic head for controlling the height of the magneto-resistive effect elements with high accuracy.
In recent years, the size of the magnetic disk drive has been ever on the decrease with the capacity thereof even on the increase, and small-sized magnetic disk drives using a 3.5-inch disk and 2.5-inch disk, respectively, are now the main stream. Among the magnetic heads used for these small-sized magnetic disk drives, the magnetic induction head of which the read output depends on the rotational speed of the disk has too small a disk rotational speed to produce a sufficient read output. With a magneto-resistive effect head using a magneto-resistive effect element having a resistance value changing with the magnetic field, on the other hand, the read output is not dependent on the rotational speed of the disk, and therefore a large read output can be produced. Also, the magneto-resistive effect head can produce a high read output as compared with the magnetic induction head even for the narrow tracks resulting from the high density, and therefore is considered suitable for the small size and the large capacity.
The magneto-resistive effect head is classified into a MR (magneto-resistive) head having a MR element, a GMR (giant magneto-resistive) head having a GMR element and a TMR (tunneling magneto-resistive) head having a TMR element. These magnetic heads having three different types of structure will hereinafter be referred to collectively as the MR head.
In the structure of the MR head having the highest efficiency of reproducing the information signal recorded in the disk, the magneto-resistive effect element is used exposed to the surface (hereinafter referred to as “the air bearing surface”) of the slider having the MR head mounted thereon in opposed relation to the disk to detect the resistance change of the magneto-resistive effect element in accordance with the change in the magnetic field. With the MR head with the magneto-resistive effect elements exposed to the air-bearing surface, the end of each magneto-resistive effect element is exposed to the air-bearing surface by lapping a part of the magneto-resistive effect element at the time of machining the air-bearing surface.
The size of the magneto-resistive effect element in the direction perpendicular to the air-bearing surface is called the height of the magneto-resistive effect element (MR element height). This MR element height is controlled by the lapping process. The read output of the magneto-resistive effect head changes with the MR element height. Therefore, variations of the MR element height are reflected directly in the variations in the read output of the magnetic head. For suppressing the variations of the read output of the magnetic head, it is necessary to control the MR element height with high accuracy in the lapping process.
The smaller the MR element height, the higher the performance of the magnetic head. The improved performance of the magnetic head makes it possible to detect the information recorded in the disk with higher sensitivity. Thus, the MR element height is ever on the decrease. Currently, an ordinary MR element has a height of 0.2 to 0.6 μm. The MR element height of the magnetic disk drive having an areal density of not less than 100 Gbits/in2 is said to be not more than 0.1 μm. This MR element height is considered to require the machining accuracy of ±0.02 μm (for the areal density of not less than 100 Gbits/in2).
Methods of lapping the MR element to the required height with high accuracy are described in JP-A-63-191570, JP-A-10-49824 and JP-A-10-208214. Generally in these methods, a measurement pattern (called “the electric lapping guide element”) separate from the MR element is used in the element forming process, and as a general practice, the measurement of the resistance value is converted to the MR element height. As a control method, on the other hand, the MR element heights converted from the resistance values of scores of electric lapping guide elements formed in a row bar are approximated by the quadratic curve or the quaternary curve, and the load imposed on the row bar during the lapping process is controlled in such a manner as to reduce the inclination component, the quadratic curve component and the swell component of the approximated curve.